red; nor numbers, nor even a good cause, for the French were more
numerous than the English, and were shamefully attacked by Henry V. on
their own soil. Many an argument from simple enumeration may thus be
turned into an induction of greater plausibility according to the Canon
of Agreement.

Still, in the above case, the effect (victory) is so vaguely conceived,
that a plurality of causes must be allowed for: although, e.g.,
discipline did not enable the Romans to conquer the Parthians, it may
have been their chief advantage over the Germans; and it was certainly
important to the English under Henry V. in their war with the French.

Here is another argument, somewhat similar to the above, put forward by
H. Spencer with a full consciousness of its logical character. States
that make war their chief object, he says, assume a certain type of
organisation, involving the growth of the warrior class and the
treatment of labourers as existing solely to sustain the warriors; the
complete subordination of individuals to the will of the despotic
soldier-king, their property, liberty and life being at the service of
the State; the regimentation of society not only for military but also
for civil purposes; the suppression of all private associations, etc.
This is the case in Dahomey and in Russia, and it was so at Sparta, in
Egypt, and in the empire of the Yncas. But the similarity of
organisation in these States cannot have been due to race, for they are
all of different races; nor to size, for some are small, some large; nor
to climate or other circumstances of habitat, for here again they differ
widely: the one thing they have in common is the military purpose; and
this, therefore, must be the cause of their similar organisation.
(_Political Institutions._)

By this method, then, to prove that one thing is causally connected with
another, say A with _p_, we show, first, that in all instances of _p_, A
is present; and, secondly, that any other supposable cause of _p_ may be
absent without disturbing _p_. We next come to a method the use of which
greatly strengthens the foregoing, by showing that where _p_ is absent
A is also absent, and (if possible) that A is the only supposable cause
that is always absent along with _p_.

Sec. 2. THE CANON OF THE JOINT METHOD OF AGREEMENT IN PRESENCE AND IN
ABSENCE.

_If_ (1) _two or more instances in which a phenomenon occurs have only
one other circumstance (antecedent or consequent) i